feat: Iteration 1 — 审计日志IP记录、文件上传、医护端API、小程序角色切换

Iteration 1 六项任务全部完成：

1. 审计日志IP记录 — task_local RequestInfo 自动注入 IP/user_agent
2. 文件上传服务 — multipart 上传 + ServeDir 静态文件服务
3. 医护端后端API — 医生工作台仪表盘 + 患者标签CRUD + 会话已读
4. 小程序角色切换 — 登录后根据角色跳转医护台/患者首页
5. 小程序安全加固 — secure-storage 开发模式警告
6. 讨论记录归档 — docs/discussions/

Cargo.lock

@@ -2106,6 +2106,12 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "http-range-header"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9171a2ea8a68358193d15dd5d70c1c10a2afc3e7e4c5bc92bc9f025cebd7359c"
+
 [[package]]
 name = "httparse"
 version = "1.10.1"
@@ -2692,6 +2698,16 @@ version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
+[[package]]
+name = "mime_guess"
+version = "2.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7c44f8e672c00fe5308fa235f821cb4198414e1c77935c1ab6948d3fd78550e"
+dependencies = [
+ "mime",
+ "unicase",
+]
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -4930,7 +4946,13 @@ dependencies = [
  "futures-util",
  "http",
  "http-body",
+ "http-body-util",
+ "http-range-header",
+ "httpdate",
  "iri-string",
+ "mime",
+ "mime_guess",
+ "percent-encoding",
  "pin-project-lite",
  "tokio",
  "tokio-util",
@@ -5045,6 +5067,12 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2896d95c02a80c6d6a5d6e953d479f5ddf2dfdb6a244441010e373ac0fb88971"
 
+[[package]]
+name = "unicase"
+version = "2.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
+
 [[package]]
 name = "unicode-bidi"
 version = "0.3.18"